pdf prezentacji - dr inż. Sławomir Winiarski

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Materiały informacyjne pochodzą ze
strony www.biofizyka.awf.wroc.pl
Mechanical energy fluctuations during
walking of healthy and ACL
reconstructed subjects
Sławomir Winiarski
University School of Physical Education, Wroclaw;
Biomechanics Dep.
Metabolic Cost of Walking
(a) Metabolic power (W)
running
walking
(b) Economy (J m-1)
running
walking
dr inż S.Winiarski
slow walking is very
economical,
up to about 2 m/s
minimum energy usage at
intermediate walking
speed, indicating
optimum efficiency for gait
Walking is very energy-efficient,
because of various mechanisms that
ensure the mechanical energy the body
has is passed on from one step to the next
1
Sources of Energy
1. Metabolic energy
E=E(L,f,v)
E = b + m ⋅ v 2 = 32 + 0,0050 ⋅ v 2
Ralston (1958) Bobbert (1960)
E=
E0
E0
≈
2
2
 s 2 

f
1 − 2 1 − 2  1 − v 
f u   vu 
 su  
Zarrugh (1974)
Zarrugh MY, Todd FN, Ralston HJ (1974) Optimization of energy expenditure during level walking. European
Journal of Applied Physiology 33: 293–306.
Ralston HJ (1958) Energy-speed relation and optimal speed during level walking. Internationale Zeitschrift für
angewandte Physiologie 17: 277–283.
Bobbert AC (1960) Energy expenditure in level and grade walking. Journal of Applied Physiology 15: 10151021.
2. Mechanical energy
4 forms of Mechanical Energy:
Energy:
Gravitational potential m g y
Elastic potential ½ k s2
Translational kinetic ½ m v2
Rotational kinetic ½ I ω2
Total mechanical energy is sum of all four
Elastic potential energy is usually omitted
because it cannot be measured
accurately
• Cavagna et al., 1977; Ca vagna and Margaria,1966.
• Inman (1981) Human Walking
• Griffin (1999) Walking in simulated reduced
gravity:mechanical energy fluctuations and exchange
Winter DA, Quanbur y AO, Reimer GD (1976) Analysis of instantaneous energy of normal gait. Journal of Biomechanics 9: 253-257.
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2
Gait Mechanism:
echanism: an Overview
Pendulum
endulum--like movements of the limbs give rise to two phases: swing & stance
stance;;
The forward momentum of the body gives it the necessary initial angular
velocity of rotation;
rotation;
“Inverted
Inverted”” pendulum action also involves interinter- conversion of potential and
kinetic energy, but in this case (unlike a conventional pendulum)
pendulum) KE reaches a
minimum at the midpoint of the motion, and PE is highest at that point
point;;
When reaching the endpoint of its “inverted swing”
swing” the stance leg does not
swing back, as a real inverted pendulum would, because the foot is taken off the
floor, the fulcrum transfers from the foot to the hip, and the leg
leg swings again as
a conventional pendulum.
The legs move as conventional pendulums during the swing (with a little
assistance from the hip flexors);
flexors);
stance
swing
This reduces the amount of muscle energy
needed to move the swinging leg forward;
forward;
Although the legs swing forwards much
like pendulums, they are prevented from
swinging backwards by footstrike
footstrike;;
Total Mechanical Energy Estimation - Methods
Body Segment Energy Method (Multiple Rigid
Body Method)
Method) Sum of all segmental total mechanical energies (Es)
1
1


Etotal = ∑Es = ∑ms ⋅ g ⋅ ys + ms ⋅vs2 + Is ⋅ωs2 
2
2


Body Center of Gravity Method (Single Rigid
Body Method)
Method)
2
1
Etotal = M ⋅ g ⋅ ycog + M ⋅ vcog
2
Inverse Dynamics and Joint Power Analysis
Method Integral of Power with respect of Time Elftman (1939), Winter (1987)
Winter DA, Quanbury AO, Reimer GD (1976) Analysis of instantaneous energy of normal gait. Journal of Biomechanics 9: 253-257
Cav agna GA, Thys H, Zamboni A (1976) The sources of external work in level walking and running. Journal of Physiology 262: 639-657
Winter DA (1979) A new definition of mechanical work done in human movement . Journal of Applied Physiology 46: 79-83.
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3
Relation to
to Other Mechanical Variables
External Work = change in body total
mechanical energy:
Wext
ext..=∆ Etotal=Etotal(tfinal)-Etotal(tinitial)
Internal Work = mechanical cost of moving the
limbs during a cyclic motion;
motion; energy transfer from
segment to segment;
Wint.=Σ |∆Etotal|- Wext
ext..
Pierrynow ski MR, Winter DA, Norman RW (1980) Transfers of mechanical energy within the total body and mechanical efficiency during treadmill walking.
Ergonomics 23: 147-156.
Robertson DGE, Winter DA (1980) Mechanical energy generation, absorption and transfer amongst segments during walking. Journal of Biomechanics 139:
845-854.
Williams KR (1985) The relationship between mechanical and physiological energy estimates. Med Sci Sports Exercise 17: 317-325.
Elftman H (1939) Forces and energy changes in the leg during walking. American Journal of Physiology 125: 339-356.
Winter DA (1987) Mechanical power in human movement: generation, absorption and transfer. Med Sci Sports Exercise 25: 34-45.
Aissaoui R, Allard P, Junqua A, Frossard L, Duhaime M (1996) Internal work estimation in three-dimensional gait analysis. Medical and Biological
Engineering and Computing 34(6): 467-471.
Energy Transfer Between Segments
Winter DA (1979) A new definition of mechanical work done in human movement . Journal of Applied Physiology 46: 79-83.
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4
Aim of Work
to
explore the possibilities of employing
the total mechanical energy into estimating
the mechanical cost of transport in normal
and pathological human gait
Material
total of 130 barebare-foot subjects
53 male (age 31,5±
31,5±9,7);
Test Group patients after ACL-reconstruction
following physiotherapy process
23 male (age 22,1±
22,1±3,2);
Control Group with no visible locomotor
impairment
Test patients underwent original physiotherapy process [Czamara, 2002] after the
isolated ACL reconstruction, which involved harvesting the tendon graft (ST or GR) and
rigid fixation.
Three Stages of physiotherapy process:
1. 2–4 weeks postoperatively;
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5
Instrumentation
SIMI Motion Analysis System (Simi Reality Motion Systems GmbH, Unterschleissheim, Germany)
I®
SIM
ISO quality standards: ISO 9001:2001
Anthropometric Model
Clauser’
Clauser’s Model
14 rigid segments
Clauser, McConv ille, Young (1969) Weight, volume and centre of mass of segments of the human body, AMRL-TR-69-70, Wright-Patterson Air Force Base.
Chandler, Clauser, McConville, Young (1975) Investigation of inertial properties of the human body, AMRL-TR-74-137 Wright-Patterson Air Force Base.
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6
Data Analysis
1.
2.
3.
4.
5.
Registering the positions of CoG for each segment;
Calculating the position of BCoG for every frame;
Calculating the height and speed of BCoG;
BCoG;
Calculating the potential and horizontal kinetic energy
of BCoG;
BCoG;
mg ⋅ hBCoG
h
norm
norm
E norm
= hBCoG
hBCoG
= BCoG
pot. =
Normalization
m⋅ g ⋅L
L
2
norm
k inet.
E
norm
total
E
2
0,5 ⋅ m ⋅ v BCoG v BCoG
=
=
m⋅ g ⋅L
2 gL
=
E pot. + E k inet.
m⋅ g ⋅ L
2
=h
norm
BCoG
v
+ BCoG
2 gL
Hof (1996) ; Sutherland (1996) ; Stansfield i wsp. (2001) ; Stansfield i wsp. (2006)
Data Evaluation
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7
Results
Potential energy, mean±
mean±SD,
SD, men
Normal (reference) group
ACL-reconstructed group
S tage 1
0,568
0,562
0,558
0,556
0,554
0,550
0,550
0,544
0,546
0,538
0,542
0,532
% Gait Cycle
0,538
% Gait Cycle
Results
Potential Energy in physiotherapy process
0,568
0,562
0,556
ACL 1
0,550
ACL 2
ACL 3
0,544
CG
0,538
0,532
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% Gait Cycle
8
Results
Kinetic Energy,
Energy, mean±
mean±SD, men
Normal (reference) group
0,0385
ACL-reconstructed group
S tage 1
0,0030
0,0380
0,0028
0,0375
0,0026
0,0370
0,0024
0,0022
0,0365
0,0020
0,0360
0,0355
0,0018
% Gait Cycle
0,0016
Results
Kinetic Energy in physiotherapy process
ACL 1
ACL 2
ACL 3
CG
% Gait Cycle
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9
Conclusions
dr inż S.Winiarski
Normal energy curves similar to Winter (1979),
(1979), Griffin (1999) and Gider et
al. (1995);
(1995);
Kinetic Energy is ca. 9 times lower then Potential Energy for the
the Control
Group;
Potential Energy, Kinetic Energy and Total Mechanical Energy rises
rises during
physiotherapy process;
Potential Energy is rising during physiotherapy process due to rising
rising
amplitude of BCoG trajectory;
Potential Energy on stage 3 of physiotherapy is significantly lower
lower then in
control group;
Mechanical Cost is lower for ACLACL-reconstructed group then for control
group;
On the stage 3 of physiotherapy Mechanical Cost is still lower then
then in control
group due to the significant lower amplitude of BCoG trajectory;
10

pdf prezentacji - dr inż. Sławomir Winiarski

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